Radiation-sensitive resistor



1955 E. H. MUELLER RADIATION-SENSITIVE RESISTOR Filed Jan. 17, 1955 FIG.3

INVENTOR EMIL H. MUELLER I BY ATTORNEY United States PatentRADIATION-SENSITIVE RESISTOR Emil H. Mueller, Watertown, Mass., troni'csCorporation of America, corporation of Massachusetts assignor to Elec-Cambridge, Mass, 2

This invention relates to radiation-sensitive targets comprising aplurality of radiation-sensitive elements formed by separate sections ofa radiation-sensitive coating applied to a nonconductive surface.Radiation-sensitive targets of this type are generally used to produce aunique electrical response when a beam of radiation, such as light, isfocused on a given element of the target. When such targets comprisevery small elements finely separated by means of grooves or scribelines, some difficulties may be encountered in making good electricalconnections to the separate elements of the target.

It is an object of this invention to provide a radiationsensitive targetof the above type which is constructed so as to provide convenient meansof making good electrical connections to the separateradiation-sensitive elements of the target.

Other and incidental objects of this invention will be apparent to thoseskilled in the art from a reading of the following specification and aninspection of the accompanying drawings in which:

Figure 1 is a View in perspective of a radiation-sensitive targetcomprising only six elements and which will serve as a large scaleillustration of the present invention;

Figure 2 is a cross-sectional view of the radiation-sensitive target ofFigure 1 taken along the lines A-A;

Figure 3 is a cross-sectional view of the radiationsensitive target ofFigure 1 taken along the lines B-B; and

Figure 4 is a view in perspective of a radiation-sensitive target inaccordance with this invention and comprising thirty-two separateradiation-sensitive elements.

It is contemplated that radiation-sensitive targets in accordance withthis invention will comprise many very small radiation-sensitiveelements having widths of the order of one hundredth of an inch or less.However, for the sake of simplicity, this invention will be described indetail with reference to Figure 1 which shows a radiation-sensitivetarget having only six radiation-sensitive elements, each of which has awidth of approximately one sixteenth of an inch.

Referring now to Figure 1, the radiation-sensitive target comprises abody structure in the form of a plate 11. The length and width of plate11 are determined mainly by the number, size, and shape of theradiation-sensitive elements to be applied to its surface, and thethickness of plate 11 is determined by the mechanical strength requiredby the target structure. A thickness comparable to that of single windowglass has been found satisfactory for usual applications. Plate 11 ismade of an electrically insulating material such as glass.

A radiation-sensitive coating 13 is applied to a part of the surface ofplate 11. This coating may be one of activated lead sulfide. A portionof this radiation-sensitive coating is then masked while a conductivecoating 15 is applied to part of the unmasked portion of plate 11. Thisconductive coating 15 is preferably made of gold, and it covers theupper and lower portions of the radiation-sensitive coating, leavingexposed the central portion 13 of the radiation-sensitive coating. Amargin 19 is preferably left along the edges of plate 11.

Figure 2 shows plate 11 with the radiation-sensitive coating 13 appliedthereto and the conductive coating 15 which partially covers theradiation-sensitive coating. The thickness of coatings 13 and 15 isgreatly exaggerated in this Figure 2 for purposes of illustration, theiractual thickness being of the order of a few microns.

Referring again to Figure 1, the radiation-sensitive coating 13 isdivided by means of grooves or scribe lines into six radiation-sensitiveelements such as that shown as radiation-sensitive element 21.Radiation-sensitive element 21 is a thin elongated portion ofradiation-sensitive coating 13 delimited by scribe lines 23 and 25.Scribe lines 23 and 25 are shown extending slightly into the upperportion of conductive coating 15. Scribe lines 23 and 25 extend wellinto the lower portion of conductive coating 15, thus forming in thelower portion of conductive coating 15 a conductive path connected tothe radiation-sensitive element 21. A radiation-sensitive element suchas element 21 is thus part of an elec trical path comprising: the upperportion of conductive coating 15 (which forms an electrode 26 common toall the radiation-sensitive elements), the radiation-sensitive elementitself delimited by scribe lines 23 and 25, and a portion of the lowerconductive coating 15 also delimited by scribe lines 23 and 25, andwhich forms an electrode 27 for the radiation-sensitive element 21.

It is to be noted that the electrode 27 is shaped by means of scribelines 23 and 25 so that the distance between scribe lines 23 and 25 isgreater in at least part of electrode 27 than the width of theradiation-sensitive element 21. This provides in electrode 27 a fairlywide area to which a good electrical connection may easily be made asshown in Figures 1 and 3. Referring to Figure 3, a groove 29 is providedin plate 11, and a conductive wire 31 is inserted in groove 29. Theelectrical connection from the electrode 27 to wire 31 is made by meansof a dab of silver paste 33 which partially fills groove 29 and coverswire 31 and a portion of electrode 27. Similar connections are made tothe common electrode 26 and to electrodes 35, 37, 39, 41 and 43 whichare connected to radiation-sensitive elements 45, 47, 49, 51 and 53,respectively.

Additionally, there is shown in Figure 3 a glass plate 54 secured to theradiation-sensitive target by means of an adhesive coating 55. The plate54 and coating 55 protect the radiation-sensitive coating 13 from theeffects of moisture and oxidation and help holding the wires 31 inplace. The plate 54 and coating 55 should readily transmit thewavelength of radiant energy to which the radiation-sensitive coating 13is sensitive.

Figure 4 shows the general configuration of a thirtytwo element cell inaccordance with the present invention. Here again the width of theradiation-sensitive element is somewhat exaggerated, as it iscontemplated that in practice it will have a width of the order of onehundredth of an inch or less. Each of the radiation-sensitive elementsis electrically connected to the common electrode 26 and to a separatelower electrode such as electrode 57. Conductive wires are connected toeach electrode in the same manner as wire 31.

The operation of the radiation-sensitive target in accordance with theinvention is as follows: when radiation impinges upon a givenradiation-sensitive element, there occurs a change in the electricalresistance of the path between the common electrode 26 and the separatelower electrode (such as electrode 27) corresponding to that element.This change of resistance may be used in ways well known to thoseskilled in the art to indicate how much radiation impinges upon whichelement of the radiation-sensitive target.

I claim:

1. A radiation-sensitive target comprising a surface ofelectrically-insulating material, a radiation-sensitive coating appliedto a part of said surface, a conductive coating applied over saidradiation-sensitive coating and leaving exposed a portion of saidradiation-sensitive coating, insulating scribe lines separating theexposed portion of said radiation-sensitive coating into a plurality ofradiation-sensitive elements and extending into said conductive coating,the distance between two scribe lines separating a givenradiation-sensitive element being greater in at least part of saidconductive coating than it is in the exposed portion of saidradiation-sensitive coating.

2. A radiation-sensitive target comprising a surface ofelectrically-insulating material, a radiation-sensitive coating appliedto a part of said surface, a conductive coating applied over saidradiation-sensitive coating and leaving exposed a portion of saidradiation-sensitive coating, insulating scribe lines separating theexposed portion of said radiation-sensitive coating into a plurality ofradiationsensitive elements and extending into said conductive coating,said scribe lines forming a plurality of distinct conductive paths froma part of said conductive coating through a radiation-sensitive elementto another part of said conductive coating, the distance between twoscribe lines separating a given radiation-sensitive section beinggreater in at least part of said conductive coating than it is in theexposed portion of said radiation-sensitive coating.

No references cited.

1. A RADIATION-SENSITIVE TARGET COMPRISING A SURFACE OFELECTRICALLY-INSULATING MATERIAL, A RADIATION-SENSITIVE COATING APPLIEDTO A PART OF SAID SURFACE, A CONDUCTIVE COATING APPLIED OVER SAIDRADIATION-SENSITIVE COATING AND LEAVING EXPOSED A PORTION OF SAIDRADIATION-SENSITIVE COATING, INSULATING SCRIBE LINES SEPARATING THEEXPOSED PORTION OF SAID RADIATION-SENSITIVE COATING INTO A PLURALITY ORRADIATION-SENSITIVE ELEMENTS AND EXTENDING INTO SAID CONDUCTIVE COATING,THE DISTANCE BETWEEN TWO SCRIBE LINES SEPARATING A GIVENRADIATION-SENSITIVE ELEMENT BEING GREATER IN AT LEAST PART OF SAIDCONDUCTIVE COATING THAN IT IS THE EXPOSED PORTION OF SAIDRADIATION-SENSITIVE COATING.